Process for producing aluminium hydrate.



CHARLES A. DOBEM'US, of NEW YORK, N. Y., ASSIGNOR OF ONE-HALE TO JOHN I SHERMAN HOYT, OF DARIEN, CONNECTICUT.

PROCESS FOR PRODUCING ALUMINIUM HYDRATE.

No Drawing.

To all whom it may concern:

Be it known that I, CHARLES A. DOREMUS,

a citizen of the United. States, and a resident of New 'York, county of New York, and State of New York, have invented certain new and. useful Improvements in Processes for Producing Aluminium Hydrate, of

which the following is a specification.

My invention relates -to the manufacture of aluminium hydrate Several processes are now known for obtaming alummlum fluorid in a cheap and simple manner, for instance, the process de scribed in my copendmg application Serial No. 7 49,806, filed February 21st, 1913. However, much difiiculty has been experienced in obtaining a process for decomposing-it in a simple, cheap and eflicient manner, to obtain valuable products, since aluminium fluorid ofiers difficulties when acted. on by chemical .reagents which decompose other aluminous salts with ease. Thus when either solid aluminium fluorid or its solution is treated with sulfuric acid a complete decomposition only results. after several evaporations, and

the use of an excess of acid. The fluorid also has a tendency to form complex salts. In carrying out my invention, I treat a solution of aluminium fluorid with an alkali,

hydrate, which increases until about 75% of.

the aluminium present in the sodium aluminate separates in the form of hydrate. This precipitate is then separated from the liquor by filtration and washed, and is suitable for,

the preparation of aluminium or aluminous products.

The recovered alkaline hquor may be used Specification of Letters Patent.

from aluminium- Patented Feb. 13, 191 7.

Application filed February 27, 1914. Serial No. 821,564.

as a solvent for-more aluminium hydrate.

precipitated, as above described.

As an example of my method of treatment I take hydro-fluoric acid of 16% strength,

and add suflicient kaolin, calcined if necessary, to neutralize the acid and precipitate silica and produce aluminium fluorid in solution. The solution of aluminium fluorid is separated from the silica by filtration. Or the aluminium'fluorid may be produced as described in my said copending application Serial No. 7 49,806. After. oxidizing any iron present in the aluminium fluorid solution in a ferrous state to ferric state, as by adding a little chlorin or peroxid' of hydrogen or other oxidizing agent l add, while stirring, enough sodium or calcium hydrate to com blue with the fiuorin in the solution to form sodium or calcium fluorid, as the case may be. Aluminium hydrate is simultaneously formed, and both are precipitated along with the iron. Sodium hydrate is next added until the aluminium hydrate has dissolved, forming a solution of sodium aluminate having about grams of Na O and 60 grams of A1 0 per liter in it. This solution is separated from the precipitated fluorid of sodium or calcium and iron by sedimentation or filtration. The precipitate is washed with as little water as possible. The filtrate is next agitated or stirred for some hours whilecold, and aluminium hydrate is precipitated which is separated from the liquor by filtration. This hydrate is also Washed to remove adherent alkali.

If the precipitate of sodium or calcium fluorid contains iron I wash it with dilute hydrofluoric. acid, thus dissolving out the iron, and follow alkali.

The ferruginous precipitate readily parts with theiron when acted on by dilute hydrofluoric acid.-. The residual fluorid after washing may then be treated, if need be, with alkali to render it neutral.

The sodium aluminate solution instead of being stirred to precipitate the aluminium hydrate may be treated with carbon dioxid the acid by water or dilute gas to decompose it and the aluminium hydrate precipitated, which by filtration and washing may be separatedlfrom the solution A of sodium carbonate simultaneously pr'o-.

duced. The sodium carbonate solution may then be causticized by lime, but this alternative method of securing the aluminium hydrate is not as direct and advantageous as the stirring.

What I claim and desire tosecure by Letters Patent is:

1. The process of producing aluminium hydrate from aluminium fluorid, which consists in treating a solution of aluminium fluorid with alkali to precipitate aluminium hydrate and a fluorid, then adding sodium hydrate to form sodium aluminate in solution, separating this 'from the fluorid precipitate, then treating the solution of sodium aluminate to precipitate aluminium hydrate, and separating the aluminium hydrate from the alkaline solution.

2. The process of producing aluminium hydrate from aluminium fluorid, which consists in treating a solution of aluminium fluorid with calcium hydrate-to precipitate aluminium hydrate and a fluorid, then adding sodium hydrate toform sodium aluminatein solution, separating this fromthe" fluorid precipitate, then treating the solu-' tion of sodium aluminate to precipitate aluminium hydrate, and separating the aluminium hydrate from the alkaline solution.

3. The process of'producing aluminium hydrate from aluminium fluorid, which consists in oxidizing any iron in a solution of aluminium fluorid, treating the solution with alkali to precipitate aluminium hydrate aluminium fluorid, treating the solution with alkali to precipitate aluminium hydrate and a fluorid, then adding sodium hydrate to form sodium aluminate in solution, separating this from the fluorid precipitate, then treating the solution of sodium aluminate to precipitate aluminium hydrate, and separating the aluminium hydrate from the alkaline solution. a

5. The process of -producing aluminium hydrate from aluminium fluorid, which consists in oxidizing any iron in a solution of aluminium fluorid, treating the solution with alkali to precipitate aluminium hydrate and a fluorid, then adding sodium hydrate to .form sodium aluminate in solution, separating this from the fluorid precipitate, then treating the solution of sodium aluminate to precipitate aluminium hydrate, and separating the aluminium hydrate from the alkaline solution. I

In testimony whereof, I have signed my name to this specification, in the presence of two subscribingwitnesses. CHARLES A. DOREMUS.

Witnewes: t

J OHN, O. GEMPLER, EDWIN Susan. 

